Wheat Yield and Yield Stability of Eight Dryland Crop Rotations

The winter wheat (Triticum aestivum L.)-fallow (WF) dryland production system employed in the Central Great Plains has evolved in the past 40 yr to include a diversity of other crops, with a reduction in fallow frequency. Wheat remains the base crop for essentially all cropping systems. Decisions to change a farming system benefit from information about average wheat yields, yield stability, and probabilities of obtaining a specified minimum wheat yield. The objective of this experiment was to quantify wheat yields, yield stability, and the probability of obtaining a specified minimum yield in eight dryland rotational systems varying in cropping intensity. The study was conducted over a 24-yr period at Akron, CO. Yield stability was characterized with six stability measures. The probability of obtaining a yield less than 1500 kg ha(-1) was also calculated for each rotation. Wheat yields were greatest in rotations where wheat followed a fallow period and least where wheat followed millet production. Rotations ranked from most stable to least stable wheat production (averaged over the six stability measures) were WF(NT), WF(CT), WMF, WCMP, WCM, WCMF, WM, and WCF. The probability of producing <1500 kg ha(-1) was very low for rotations with wheat following fallow (about 0.03) and much higher for wheat following pea (0.35) or millet (0.48-0.58). The study results identified the WMF rotation as an intensified rotation with relatively high average wheat yields and yield stability.